Recording the brainstem's response to sound has long been established as a valid and reliable means to assess the integrity of the neural transmission of acoustic stimuli. Transient acoustic events induce a pattern of voltage fluctuations in the brainstem resulting in a familiar waveform that yields information about brainstem nuclei along the ascending central auditory pathway. Accurate stimulus timing in the auditory brainstem is a hallmark of normal perception.
Abnormal perception, understanding and processing of spoken language are fundamental criteria in the diagnosis of many learning disabilities. Currently, central auditory processing disorders are diagnosed through a central auditory processing (CAP) evaluation. Audiologists and speech-language pathologists perform a series of tests, all of which are perceptual and/or audiological in nature, i.e. subjective—not physiological or objective. Auditory brainstem response (ABR) testing provides a physiological indication, but no connection has been established between conventional ABR results and learning disabilities.
Children and adults diagnosed with learning disabilities exhibit highly variable subject profiles. Many factors can contribute to current diagnosis of a learning problem. These include variations in: basic perceptual physiology and higher levels of cognitive function and attention, experientially developed compensatory mechanisms, exposure to previous remedial interventions and differing interpretations of diagnostic categories by clinicians. A consistent and reliable method for diagnosing individuals with learning disabilities has yet to be established.